Having spent perhaps a grand on backup kit over the years (including 440 quid to recover a crashed hard drive) this hurt. In the hope it helps at least one person to avoid similar problems, here's the tale:-
- The backup drive (NAS, at the other end of the house, connected by ethernet-over-mains) needs restarting manually after any power cut. I'd forgotten to do this. (We get a lot of power cuts. I read somewhere that the airport takes priority when suppliers are low, and on balance I'd prefer them to keep the runway lights on. Even if I'm not flying!)
- The backup software didn't tell me. I assume if it can't see the drive (which was still switched off) it assumes I know what I'd doing. And I assumed it would tell me.
- As far as I can tell the NAS drive got full sometime along the way. On previous occasions I'm sure it warned me, but - perhaps coincidentally ...
- The backup software broke.
Bit of a fright, and quite a time sponge to sort through all the causes and get back to some sort of stability. Along the way I found Gina Trapani's excellent HowTo at lifehacker.com/147855/geek-to-live--automatically-back-up-your-hard-drive
When it's a new, strange or forgotten area, I need instructions to start from what I don't know, not what the author does. And she did. Written Jan 2006, the page has had over half a million hits. She deserves every one.